Coating composition containing vinylidene chloride acrylonitrile copolymer and a halogenated hydrocarbon as a gel retardant therefor



Fatented July 5, 1949 UNlTED s'mras PAE/NT orrlca COATING COMPOSITIONCONTAINING VI- NYLIDENE CHLORIDE ACRYLONITRILE COPOLYMER AND AHALOGENATED HY- DROCARBON AS A GEL RETABDANT THEREFOR Paul MatthewHauser, Kenmore, N. Y., asslgnor to E. I. du Pont de Nemours & Company.Wilmington, Del., a corporation of Delaware No Drawing. ApplicationApril19, 1946,

Serial No. 663,629

3 Claims.

at moderately low temperatures and hence are particularly suitable forthe coating of transparent, non-fibrous, synthetic film such asregenerated cellulose film and the like to produce moistureproof,heat-scalable wrapping tissue, etc. The difliculty, howeven'with theaforesaid solutions is that they gel rapidly at temperatures below 60 C.and this behavior makes coating in conventional equipment very difficultsince gelled solutions cannot be doctored readily into smooth continuouscoatings.

Therefore, an object of this invention is to provide means forinhibiting the gelation and improving the coatability of methyl ethylketone solutions of vinylidene chloride-acrylonitrile copolymers whereinthe vinylidene chloride content is at least 90% by weight.

Another object is to provide methyl ethyl ketone solutions of vinylidenechloride acrylonitrile copolymers wherein the vinylidene chloridecontent is at least 90% by weight, which solutions are resistant togelling at temperatures below 60 C.

A still further object is to provide a methyl ethyl ketone solution ofvinylidene chloride acrylonitrile copolymer wherein the vinylidenechloride content is at least 90% by weight, which solutions can beapplied to regenerated cellulose and the like in conventional coatingsystems operated at normal temperatures. These and additional objectiveswill more clearly appear hereinafter.

at temperatures below 60 C. is retarded to the point where it is usablein conventional coating The preparation of methyl ethyl ketone-solublecopolymers of vinylidene chloride and acrylonitrile wherein the weightratio of vinylidene chloride to acrylonitrile is at least 4:1, isdescribed and claimed in the copending U. S. patent application ofChester R. Hardt, Serial No. 605,185, July 14, 1945, now abandoned.Methyl ethyl ketone solubility is achieved in accordance with saiddisclosure by efiectlng the copolymerization of vinylidene chloride andacrylonitrlle, in any convenient manner, in the presence of a smallamount of modifier of the iormula wherein R and R may each be hydrogenor a hydrocarbon group.

Any halogenated hydrocarbon, the dipole moment of which is within therange of 0 and 0.8

of a Debye unit, is useful for purposes of my invention. Asrepresentative compounds there may be mentioned carbon tetrachloride,hexachloroethane, hexachlorcyclohexane, pentaerythritol tetrabromlde,pentaerythrito1 tetraiodide, trans-1,2-dichloroethy1ene,tetrafluorethylene, 1,3,5-tribrombenzene, p-dichlorobenzene,p,p'-dichlorodiphenyl, etc. The amount of symmetrical halogenatedhydrocarbon employed may vary within wide limits, but it should not, ofcourse, be used in amounts which would interfere with the desirablesolvent action of the methyl ethyl ketone. Amounts as small as 2% basedon the weight of total solvents efiectively retard gelation of thesolvent. Preferably the ge1 retardants of this invention should be usedin amounts within the range of 10% to 20% by weight based on the weightof total solvent.

As indicated previously, the improved coating compositions of myinvention can be applied by any conventional means and at temperatureswhich normally obtain in the conventional coating systems.

The following example, wherein is set forth aspecific embodiment,further illustrates my invention. Parts and percentages are by weightunless otherwise indicated.

' .ti-i I A composition consisting of:

was coated on regenerated cellulose 5:3. in a 3 coating tower at 30 C.There was no indication of gelation after 10 minutes. A continuous,clear, moisture-impermeable coating was produced.

In contrast, a coating composition identical with the above save thatcarbon tetrachloride was replaced with methyl ethyl ketone was appliedto regenerated cellulose film in the same way. A discontinuousmoisture-permeable coating resulted. The coating composition gelledrapidly even at 50 C.

From the above example it will be apparent that by means of the presentinvention the costability of vinylidene chloride-acrylonitrilecopolymers containing at least 90% vinylidene chloride, is greatlyimproved and one is now enabled to employ such polymers in conventionalcoating systems whereby to produce clear, flexible, moisture-impermeablecoated film of excellent quality. Also, self-sustaining film ofvinylidene chioride-acrylonitrile copolymer may similarly be prepared bycasting the solution onto a suitable surface and stripping the dried orsolvent-free film therefrom as in the usual methd of dry-casting.

As many widely different embodiments can be made without departing fromthe spirit and scope of my invention, it is to be understood that it isnot restricted except as set forth in the appended claims.

I claim:

1. A film-forming composition comprising essentlally a copolymer ofvinylidene chloride and acrylonitrile wherein the weight ratio oivinylidene chloride to acrylonitrile is at least 4:1 and the remainderof the copolymer is acrylonltrile. dissolved in methyl ethyl ketonecontaining from 2 to 20% by weight or halogenated hydrocarbon to retardgelatlon o! the composition, said halogenated hydrocarbon having adipole moment oi from 0 to 0.8 of a Debye unit.

2. A film-forming composition comprising essentially a copolymer ofvinylidene chloride and acrylonitrile wherein the weight ratio ofvinylidene chloride to acrylonitrile is at least 4:1 and the remainderoi the copolymer is acrylonitrile. dissolved in a solvent mixtureconsisting of to by weight 01' methyl ethyl ketone and 20% to 10% byweight of halogenated hydrocarbon, having a dipole moment of from 0 to0.8 of a Debye unit.

3. The film-forming composition of claim 2 wherein the halogenatedhydrocarbon is carbon tetrachloride.

PAUL MATTHEW HAUBER.

REFERENCES CITED UNITED STATES PATENTS Name Date Tucker Apr. 13. 1943Number

